Timepieces, which are able to provide, in addition to the current time, at least two time-related indications, such as the date and the day of the week are already known in the state of the art. One example of this type of timepiece is shown with reference to FIGS. 1 and 2, annexed to this Patent Application and which respectively show a plan view of the timepiece dial and a plan view of the time quantity display mechanism.
Designated as a whole by the general reference numeral 3, the timepiece includes at the centre thereof a set of time zone hands, formed by an hour hand 5a, a minute hand 5b and a second hand 5c, which move above a circular dial 7. The time zone mechanism has already been disclosed in EP Patent Application No. 1544691 in the name of the Applicant and will not, therefore, be described further here.
The timepiece whose time quantity display mechanism is shown in plan in FIG. 2 is a time zone watch including a retrograde 24-hour display for the local time of the place where the wearer of the watch usually lives and a 12-hour display for the time zone of the place where the wearer of the watch is staying temporarily.
Watch 3 is completed by:                a retrograde date display formed by a hand 9a, which moves opposite a scale 9b in the shape of an arc of a circle extending between the “1st” and the “31st”;        a retrograde day of the week display, formed by a hand that moves along a scale 11b marked from “Monday” to “Sunday”;        a retrograde 24-hour display formed by a hand 13a that moves along a scale 13b in the shape of an arc of a circle extending between “0” and “24”.        
The watch display is completed by a small seconds indication 15.
As can be seen in FIG. 2, the time quantity display mechanism includes, in particular, at the centre thereof, an intermediate wheel 1, which is secured to an hour wheel 1a. In other words, intermediate wheel 1 rotates clockwise and completes one revolution in twelve hours. This intermediate wheel 1 meshes with a date drive wheel 2, which rotates anticlockwise at the rate of one revolution in twenty-four hours. This date drive wheel 2 carries a finger 4, via which it drives, at the rate of one step per day, a date wheel 6, which is indexed by a jumper spring 8, and which carries a cam 10. At one place on the profile thereof, cam 10 has a steep side 12, which marks the change between the date of the last day of a given month and the date of the first day of the following month, in other words between the “31st” day of one month and the “1st” day of the next month.
The time quantity display mechanism is completed by a control lever 14, provided at one end thereof with an arm 16, via which the lever abuts against cam 10 in a normal operating period, and including at the other end thereof a rack 18, via which it meshes with the date display wheel 20, which carries the date indicator 9a (not visible in FIG. 2). The control lever 14 is pivoted at 22, whereas a second lever 24, called the return lever, is pivoted at 26. This return lever 24 has a similar structure to that of control lever 14, including, in particular, a rack 28, via which it meshes with the date display wheel 20. As can be seen upon examining FIG. 2, return lever 24 is biased by spring element 30, which tends to rotate the lever clockwise. In turn, return lever 24 tends thus to rotate control lever 14 clockwise and to hold arm 16 thereof abutting against the profile of cam 10.
As can be seen upon examining the drawing, in the example shown, spring element 30 is integral with return lever 24 and abuts against a stop member 32 for pre-winding. In order to achieve this result, the lever could, for example, be made via a LIGA photoetching technique. It goes without saying, however, that spring element 30 could be made in the form of a separate part from return lever 24.
In addition to the date display device, the time quantity display mechanism shown in FIG. 2 includes a day of the week display device, which has essentially the same structure as the date display device. More specifically, this day of the week display mechanism includes a day drive wheel 2a, which rotates anticlockwise, driven by intermediate wheel 1. This day drive wheel 2a carries a finger 4a via which it drives, at a rate of one step per day, a day wheel 6a, which includes fourteen teeth and which thus completes one revolution in fourteen days. Thus, day wheel 6a carries a cam 10a, which has a double cam profile with two steep sides 12a1 and 12a2, which are symmetrical relative to the geometrical centre of said cam 10a. Each of the two steep sides 12a1 and 12a2 of cam 10a marks the change of the day indicator from the last day of one week to the first day of the following week, namely from Sunday to Monday. It will be noted that day wheel 6a is indexed by a jumper spring 8a. 
The day display device is completed by a control lever 14a, which, via arm 16a thereof, abuts against the profile of cam 10a and which meshes, via rack 18a thereof, with a day display wheel 20a. A return lever 24a is also provided, stressed by a spring 30a and which, at one end thereof, includes a rack 28a, via which it meshes with the day display wheel 20a. 
It has already been specified above that the watch also includes a 24-hour local time display. Consequently, when the position of the hour and minute hands is set, the 24-hour indication must also be set. Thus, the 24-hour display device includes an intermediate wheel 34, driven by the watch movement and which meshes with a 24-hour wheel 6b, which carries a cam 10b. At one place on the profile thereof, this cam 10b has a steep side 12b, which marks the change from the twenty-fourth hour of one day to the first hour of the following day. A control lever 14b abuts, via arm 16b thereof, against the profile of cam 10b and meshes with a 24-hour display wheel via rack 18b thereof. Likewise, a return lever 24b, biased by a spring element 30b, meshes, via rack 28b thereof, with 24-hour display wheel 20b. 
A watch fitted with a single time quantity indication device, such as a watch that has only a current time display hand set and one date indicator hand, does not raise any particular problems. Indeed, the accuracy of the date display jump from one date indication to the next date indication around midnight is guaranteed by the accuracy with which the date indicator hand is driven onto its arbour.
The same is not true of a watch that includes, for example, a 24-hour display and a date display device with hands. Indeed, in such case, when the watch is assembled, one must ensure that arm 16b of control lever 14b has actually dropped along the steep side 12b of cam 10b. This position of arm 16b of control lever 14b corresponds exactly to midnight. Once one has ensured that arm 16b has indeed dropped along the side 12b of cam 10b, the 24-hour display indicator hand can then be driven precisely into place. Next, as the date drive wheel 2 has already been assembled, the centre wheel 1a and its intermediate wheel 1 are assembled. Since the kinematic connection between centre wheel 1a and intermediate wheel 34, and between centre wheel 1a and date drive wheel 2, is not the same, there may be a shift of one or several teeth between intermediate wheel 1 and date drive wheel 2. The result of this shift between the toothings of intermediate wheel 1 and plate 5 of date drive wheel 2, is that a time difference of up to 15 to 20 minutes may be observed between the jump at midnight of the 24 hour display and that of the date display device.
The same problem arises with a watch including two time quantity display devices, such as the date indication and the day of the week indication. When arm 16 of control lever 14 has dropped along steep side 12 of cam 10, we know that it is midnight. The current time display hand and the date indicator hand can then be precisely driven into place. However, since the kinematic connections between intermediate wheel 1 and date drive wheel 2, and between intermediate wheel 1 and day drive wheel 2a, are not the same, there may be a difference of several minutes between the jumps of the date indicator hand and the day indicator hand.
It will be clear that such differences between the jumps of the indicator hands for the different time quantities are not appreciated by the wearer of the watch.
It is an object of the present invention to overcome this problem by providing a mechanism that can adjust, with precision, the moment at which a time quantity display device in a timepiece jumps.